Energy and Materials Recovery from Municipal Solid Wastes at the Island of Rhodes

Transcription

1 Energy and Materials Recovery from Municipal Solid Wastes at the Island of Rhodes N.J. Themelis 1, Athena Bourka 2, and George Ypsilantis 3 1 Earth Engineering Center, Columbia University, New York, NY 10027, U.S.A. 2 EPTA Environmental Consultants-Engineers, Olofytou 15, Athens 11142, Greece 3 Municipal Waste Management Co. of Rhodes (DEKR), P.O. Box 407, Rhodes 85100, Greece * Corresponding author njt1@columbia.edu Abstract The Earth Engineering Center of Columbia University, the engineering company EPTA, and the municipal waste management company of Rhodes (DEKR) collaborated on the pre- feasibility study and design of a waste-to-energy (WTE) plant that will recover energy and metals by combusting the post-recycling municipal solid wastes (MSW) of the ten municipalities of Rhodes. These wastes are now disposed in a landfill that has a projected life of only three years. The specified requirements of Rhodes were for a thermal treatment technology that is widely used and fully proven. The only waste-to-energy method that met these specifications is controlled combustion of as-received MSW on a moving grate, also known as mass burning. Currently, Rhodes generates 102,000 tons of MSW per year and the generation varies considerably between winter and summer months due to tourism. The site selected for the proposed environmental park is adjacent to the existing landfill in northern Rhodes and will include a materials recovery facility (MRF) for recycling, the waste-to-energy (WTE) plant, and a visitor s center. The preliminary configuration of the WTE facility consists of two parallel lines of 10 tons/hour each, that is a total of 160,000 tons of MSW per year. The Air Pollution Control (APC) system will be state-of-the-art and will include a dry scrubber for removing acid gases, activated carbon injection to capture volatile metals and dioxins, selective non-catalytic reduction (SNCR) of NOx, and removal of particulate matter in a fabric filter baghouse. The stack emissions will be monitored continuously and are projected to be well below the EU standards. The engineering, environmental, and economic aspects of the proposed WTE plant are discussed in this paper. Keywords: Rhodes, Greece, waste management, waste-to-energy, WTE, thermal treatment, municipal solid wastes, MSW, island 1. INTRODUCTION In February 2008, the Waste Management Company of Rhodes (DEKR), requested Themelis Associates and the Earth Engineering Center of Columbia University to conduct this prefeasibility study. The study was divided into two parts: Themelis Associates undertook the selection of the most suitable technology and the estimate of WTE plant capacity, dimensions and plant layout, personnel and materials needs, and preliminary capital and operating costs. EPTA Environmental Consultants were engaged to prepare the preliminary design of the Environmental Park (Eco-Park Rhodes) and the preliminary Environmental Impact Statement

2 that has been submitted to the Ministry of the Environment of Greece (YPEHODE).. 2. SPECIFIED CONDITIONS FOR SELECTION OF TECHNOLOGY At the very beginning of this study, the Municipal Waste Management of the city of Rhodes (DEKR) set the following essential conditions to be met by Themelis Associates in selecting the technology to replace the existing HYTA that is projected to fill up in about three years: a) The technology selected should solve the waste management problem of the island not only for a certain number of years but for generations to come. b) The technology should be proven for several years and be widely accepted in nations that are leading in the global effort for environmental protection. c) The proposed plant should be of capacity that can handle the MSW of all ten municipalities of the island of Rhodes as well as other commercial, light industrial and agricultural residues that cannot be recycled; plus the biosolids produced by the wastewater treatment plants in Rhodes.. d) The proposed technology should be environmentally superior to a new HYTA. e) The proposed plant should be economically viable and not impose a very high gate fee, per ton of MSW processed, on the citizens of the island. In particular, it should conserve land by reducing the volume of residuals to be landfilled. 3. RESULTS OF STUDY There are several thermal treatment technologies that recover energy and metals from MSW and reduce its volume for disposal by at least 90%. These so-called waste-to-energy (WTE) technologies have been adopted widely in more than 600 facilities in nearly forty nations for the recovery of energy and metals from municipal solid wastes (MSW). These technologies conserve energy resources and land and also have substantial environmental benefits over landfilling, which currently is the only alternative for managing post-recycling solid wastes. The results of this study can be summarized as follows: 1. On the basis of the specified conditions by DEKR, the best suited thermal treatment technology for the first WTE facility in Greece is controlled combustion of as-received MSW on a moving grate and recovery of the energy in the combustion gases by means of a boiler and a steam turbine. This technology is called mass burn and is by far the dominant WTE technology, used in over 500 plants around the world. It was selected over some other existing WTE technologies, e.g. Refuse Derived Fuel (RDF) combustion, because of its simplicity of operation and proven performance in many WTE facilities within the E.U., of about the same size as the projected Rhodes facility. 2. The only alternative to the RDF and mass burn technologies is pre-treatment of the MSW mechanically (MT) or mechanically and biologically (MBT). However, it was concluded that since there is no co-combusting facility in Rhodes equipped with the required Air Pollution Control system to handle high chlorine and volatile metal gases,

3 both of these methods would require building an RDF-combusting plant in Rhodes, to combust the RDF product of the MT or MBT plant. This alternative has not been tested sufficiently and, also, on the basis of past experience with RDF combustion, would require a higher investment than the mass-burn WTE. 3. The emissions of the proposed WTE are projected to be a fraction of the corresponding EU standards and considerably lower than the emissions from lignite-fired power plants in Greece. For example, the total annual dioxin emissions of the two-line 160,000-ton plant were estimated at less than 0.05 grams per year of toxic-equivalent dioxins and furans. Also, in comparison to the present form of landfilling, the Greenhouse Gas emissions of the WTE plant will be lower by an estimated one ton of carbon dioxide per ton of MSW combusted rather than landfilled. 4. The proposed site of the Eco-Park in northern Rhodes was visited both by Themelis Associates and EPTA engineers and was found to be very suitable for a WTE facility, as it will improve the existing landfill area, is accessible by a highway, and is close to the electric grid line. 5. The proposed WTE plant may consist initially of one line (grate, furnace, boiler, Air Pollution Control system) of annual capacity of 80,000 tons (10 tons/h). However, the building size can provide for later expansion to two lines of 160,000 tons capacity. 6. The two-line WTE facility (160,000 tons/year) will generate an estimated 96,000 MWh of net electricity (600 kwh/ton) for the grid. There will also be available another 80,000 MWh of thermal energy which may be utilized by an adjacent industrial operation that can make use of low pressure steam, such as a paper recycling plant. 7. The capital cost of the two-line operation was estimated at 98 million and of the singleline plant 63 million. 8. The major item in the operating cost of a WTE facility is the repayment of the capital cost of its construction. As the first WTE unit in Greece, this plant may benefit from an EU grant, similar to those that have been provided for other infrastructure projects that reduced environmental impacts. 9. A preliminary estimate based on the assumptions that: a) the EU grant will amount to 30% of the capital cost of the two-line plant; b) the average price received for the electricity (about 50% of which is biomass energy and therefore renewable) will be 70 per MWh; and c) the gate fee for the MSW will be 60 per ton of MSW, showed that the projected WTE would be economically viable, during the 20-year period that the capital investment is paid off, and an economic boon to the community thereafter.

4 Figure 1 is a schematic diagram of a mass-burn WTE facility of similar design to that planned for Rhodes. Figure 1. Schematic diagram of a mass-burn WTE plant Figure 2 shows a preliminary plot plan of the waste-to-energy facility, starting with the totally enclosed tipping floor on the right, where the trucks discharge their load into the storage bunker from which claw cranes load the MSW into the feed hopper; the combustion chamber and boiler in the middle, and the turbine generator and Air Pollution Control system, on the left. Figure 2. Preliminary plot plan of Rhodes WTE This plot of land amounts to about 3.6 hectares. It is interesting to compare with the land required to landfill 3,2 million tons of MSW (160,000 tons per year times 20 years). On the

5 average, modern sanitary landfilling requires one square meter of land for every 10 tons of MSW landfilled. Therefore, a new landfill (HYTA) of 20 years lifetime would use up 32 hectares Figures 3 and 4 are photos of WTE facilities of nearly the same size as the one planned for Rhodes. These two facilities were designed by the Danish firm Ramboll who are specialists in WTE facilities and advised the Earth Engineering Center with regard to the process equipment for the Rhodes plant. It is interesting to note that Denmark, with a population of only 5 million, has 30 waste-to-energy facilities that supply electricity and district heating. Figure 3. Danish WTE facility of similar capacity (photo courtesy of Ramboll, Denmark) Figure 4. Danish WTE facility of similar capacity (photo courtesy of Ramboll, Denmark)

6 The heating value (LHV) of the Rhodes MSW ranges seasonally between 9 and 11 MJ/kg. For comparison, the average LHV of municipal solid wastes in nearly one hundred E.U. WTE plants, examined by the Confederation of European WTE Plants (CEWEP) was found to be about 9.7 MJ/kg. The following diagram, by Martin GmbH shows the wide range of MSW treated by means of the Martin grate globally. It can be seen that the entire range spans from as low as 4 MJ (China) to a high 16 MJ/kg, for mixed MSW and industrial wastes. For the purposes of this prefeasibility study, it was assumed that the Lower Heating Value of the Rhodes MSW will be 10 MJ/kg. P. Rep. of China Rep. of Korea Brazil Taiwan, R.O.C. Rep. of Singapore Japan Europe U.S.A. Switzerland Κίνα Κορέα Βραζιλία Ταϊβάν Σιγκαπούρη Ιαπωνία Ευρώπη Possible total range Up to kj/kg Figure 5. Range of heating values of MSW combusted by means of the Martin GmbH (in kj/kg) 4. RHODES ENVIRONMENTAL PARK The municipal waste management company of Rhodes (DEKR) plans to construct an integratedwaste- management Environmental Park that will include composting of source-separated organics, recycling of source-separated recyclables (mostly paper, metals and some marketable grades of plastics), combustion of post-recycling MSW, and sanitary landfilling (HYTY in Greek) of the WTE ash that is not used beneficially. Figure 6 shows the flowsheet of the Rhodes Environmental Park.

7 Figure 6. Preliminary flowsheet of integrated waste management of Rhodes municipal wastes Figure 7 is the a preliminary plot plan of the entire Environmental Park, showing the location of the eco-park offices and visitors center, the waste-to-energy facility, the composting plant, the materials recovery facility and other installations. The eco-park was designed by EPTA Environmental Consultants.

8 Figure 7. Preliminary plot plan of Environmental Park (EPTA Environmental Consultants) 5. CONCLUSIONS The first plant for the recovery of energy from municipal solid wastes in Greece is being planned for one of the most beautiful and famous islands of Greece, Rhodes (Rothos in Greek). The preliminary technical and environmental studies have been completed and the projected environmental impacts of this installation have been submitted to the Ministry of the Environment and Public Works (YPEHODE). The chosen site for this project is on the northern part of the island and is adjacent to the existing regulation landfill that is now serving most of the population of Rhodes but is scheduled to fill up in less than three years. According to the present plan of Rhodes, in addition to a state-of-the-art waste-to-energy (WTE) plant which, at the beginning, will process an estimated 300 tons of MSW per day, the Environmental Park that will be created at that site will include an aerobic composting plant for the production of soil conditioning compost, a Center for Recovery of Recyclable Materials (KDAY of Rhodes)., and a new monofill cell (HYTY in Greek) that will be used for disposal of the WTE ash that cannot be used beneficially on the island, as has been done in the island of Bermuda and many other nations. The total capital expenditure for two parallel lines of eventual total capacity of 160,000 tons of post-recycling municipal wastes per year (10 tons per hour per line maximum at 90% plant availability) was estimated at nearly 100 million euro, for two lines of 160,000 tons capacity, or 63 million euro, for one line of 80,000 tons capacity. The plant will most likely be financed as a

9 Public Private Partnership (SDIT in Greek). A special problem in Rhodes and other popular tourist destinations is that during the summer months the generation of MSW nearly doubles. To overcome this problem, the Rhodes authorities are considering the importation of MSW from other islands in the area, to complement the feedstock to the WTE plant; or the storage and use of industrial wastes from Rhodes and other places. The high capital cost of the plant is explained by the fact that in addition to eliminating the need for landfilling on the island, it will utilize the heat of combustion to generate an appreciable amount of electricity for the island, estimated up to at 96,000 MWh per year at full operating capacity. Also, it will include state of the art gas cleaning equipment consisting of dry scrubber (HCl and SO2 removal), activated carbon non-catalytic selective reduction (for NOx), activated carbon injection (for volatile metals and dioxins/furans), and fabric filter baghouse (for particulate matter). As a result of the highly sophisticated Air Pollution Control system, the projected emissions will be at lower levels than the E.U. stringent standards that are applied in nations like Denmark, Germany, France, the Netherlands, Sweden, and Switzerland. For example, the projected total emissions of dioxins and furans from the combustion of 160,000 tons of MSW annually will be 0.05 grams TEQ. Efforts are also under way to attract industrial or commercial users who can use the low-pressure steam, that remains after generating electricity in the steam turbine, to heat or cool facilities that may be built within a few kilometers of the Eco- Park site. An economic comparison of the proposed WTE with a new HYTA showed that that a new landfill for Rhodes (HYTA in Greek) would require a lower investment and, during the first ten years of operation, a lower gate fee to be paid by the citizens (40 euro per ton of MSW vs 60 euro for the WTE). However, the new HYTA would fill up in about twenty years and more land would then be required for another HYTA and so on during the 21st century. In contrast, the WTE can be maintained in such a way that, after the initial capital investment is repaid in 20 years, the plant can continue serving the population of the island and generating electricity for a very long time. In fact there are several WTE facilities in the US, e.g. the Saugus plant in northern Massachusetts, that in 2006 completed its first thirty years of operation and is now on its second thirty-year period. Therefore, the Rhodes investment in a WTE facility will conserve land and enrich the island s infrastructure for generations to come. Acknowledgements The input of Bettina Kamuk and Jorgen Haukohl of Ramboll Management Consulting ( and of Georgia Columbus (ETAE) in the Rhodes pre-feasibility study is gratefully acknowledged.

10 References 1. EPTA Environmental Consultants Προµελέτη Περιβαλλοντικών Επιπτώσεων για το Έργο: Περιβαλλοντικό Πάρκο Ρόδου Μονάδα Θερµικής Επεξεργασίας Αστικών Αποβλήτων private communication to DEKR, October Earth Engineering Center, Columbia University, Ενεργειακή Αξιοποίηση Αποβλήτων- Μονάδα Μετατροπής Αποβλήτων-Σε-Ενέργεια (WTE) µε τη Μέθοδο Μαζικής Καύσης για τους ήµους της Νήσου Ρόδου, private communication to DEKR, October Themelis, N.J., " Older and Newer Thermal Treatment Technologies from a Reaction Engineering Perspective, Conference Proceedings; International Thermal Treatment Technologies (IT3) 27th, Air & Waste Management Association, Montreal, May Themelis, N.J., The Government Role for Sustainable Waste Management in North America Paper # 178 Conference Proceedings; International Thermal Treatment Technologies (IT3) 27th, Air & Waste Management Association, Montreal, May Arsova, L. R. van Haaren., N. Goldstein, S.M. Kaufman, and N.J. Themelis, The State of Garbage in America, BioCycle (Journal of Composting & Organic Recycling), Vol. 48, No.12, pp , December Themelis, N.J., Developments in thermal treatment technologies, Proc. NAWTEC 16, Paper , NAWTEC16, Proceedings of the North American Waste to Energy Conference, Philadelphia, May Ramboll Group, Energy, 8. Martin GmbH, Munich, Germany, English 9. Georgia Columbus, M.S. Thesis, WTE for Attica, hh 10. General information about WTE applications in various countries and in Greece can be found at and